Publisher: –
Developer: Richard Greenblatt
Release date: 1966
Platform: Mainframe (PDP-6)
Type: Chess
Country: U.S.A.
More info: Great article of the game from 1969, Read more about the game and the matches
Related game: A Chess Playing Program for the IBM 7090 Computer
Alternate titles: “The Greenblatt Chess Program”, “Robert Q” — Entry name in the in the monthly Boylston Chess Club Tournament at the Young Mens Christian Union


Mac Hack VI, a.k.a. The Greenblatt Chess Program is a chess program that ran on the PDP-6. It was written in MIDAS and was the first computer program to play in a human tournament and be granted a chess rating in 1967. The game was inspired by the Kotok-McCarthy-Program, but improved upon it in design and search width.
The name Mac Hack VI comes from Project MAC a large sponsored research program located at MIT. The number VI refers to the PDP-6 machine for which it was written,


The first step was to produce a simulated chess set, whereby the computer would display the current board and accept moves in the standard chess notation through a teletype. Routines to evaluate the board, generate legal moves and perform a minimax search of a game tree.


With further developement the program played in its first tournament in February of 1967. It played in local tournaments again in March, April and May. The improvement it has shown is due to additional programming and debugging, not learning.

The program is an honorary member of the United States Chess Federation and the Massachusetts Chess Association, under the name Mac Hack Six. In the April amateur tournament the program won the class D throphy.

The computer entered the tournament under the same rules as a human cotestant. Moves was transmitted from the tournament site directly into the PDP-6 by teletype. A human operator was at the tournament, who observed the opponent’s move, typed it in using standard chess notation, received the machine’s reply, played it on the board and operated the clock. Of the two hours alloted to the machine for making the first fifty moves, about 7 minutes was lost in these operations.

The machine never offered a draw, but if the opponent offered one, the operator typed in “draw?”. The machine replied either “accept” or “decline”. If the machine became hopelessly lost, human operators resigned for it.

The program is estimated to have played in excess of 300 games in over the board competition with human players. It has played 18 tournament games.


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